As an example of a conventional electromagnet-installed actuator for a contactor, an actuator described in Patent Literature 1 (JP-A No. Hei 5-20976) is known. The actuator for a contactor described in the Patent Literature 1 is schematically formed with an electromagnet including a fixed core and a movable core, a yoke and coil, a trip spring (pulled-out spring), a wipe spring and the like.
The above-described trip spring is provided between a case side wall and a lever to which the movable core is fixed, and is employed to perform interrupting operation on a main contact of a vacuum switchgear by applying torque to the lever to rotate the lever. On the other hand, in the wipe spring, one end is connected to the lever while the other end is connected to the main contact movable member. It is pushed up by rotation of the lever, to apply contact pressure between the main contacts, thus employed to prevent adhesion of the main contacts upon closing.
Then, when the coil is excited, the movable core is attracted in the direction of the fixed core, and the main contact movable member is brought into contact with the main contact fixed member, via the lever interlocked to the movable core, in a closed status. When the excitation of the coil is stopped, by a repulsive force between the trip spring and the wipe spring in which energy has been stored during the closing operation, the main contact movable member moves in a contact parting direction, and is in an interrupted status from the main contact fixed member.
Generally, in an electromagnet-installed actuator for an contactor, when the closed status of the main contact is held, since the distance between the movable core and the fixed core is short and the magnetic resistance is low, the coil exciting power is lower than that upon closing operation of the main contact.
In the example of the above-described Patent Literature 1, the coil is excited then the movable core is attracted in the direction of the fixed core and the main contact is in the closed status. Immediately before the main contact is in the closed status, the coil exciting power upon holding of closed status is lowered by electronic circuit control so as to lower the coil energizing voltage. Otherwise, immediately before the main contact is in the closed status, the coil exciting power upon holding of closed status is lowered by circuit switching so as to serially connect the coil to a current limiting resistor. Thus energy consumption is saved.